1. Field of the Invention
The present application relates to an optical receiver adaptable to an optical system that transmits a data divided into a plurality of parts each having a wavelength specific thereto and different from others. In particular, the present application relates to an optical receiver capable of distinguishing a failure occurred in a divided part.
2. Related Background Arts
As the volume to be transmitted on a communication system explosively expands, not only the speed of the transmission but the capacity thereof have been also enhanced. An optical transceiver or an optical received implemented therein has accelerates the operational speed exceeding 10 Gbps, reaching 40 or 100 Gbps. Only one optical active device becomes hard to operate in such a high speed transmission. Accordingly, architecture to divide data into several parts and to transmit each of parts on a wavelength specific thereto has been common in the field.
For instance, a data with the speed of 100 Gbps is divided into four parts each having the speed of 25 Gbps, and four optical transmitters transmit each of the four parts carrying on a wavelength different from others in 1300 nm wavelength band. While in an optical receiver, the optical signal incoming therein is de-multiplexed into four parts each being detected by an optical device independent to each other. Thus, the total 100 Gbps transmission is realized.
However, the 1300 nm wavelength band is inherently attributed with an optical loss by the transmission medium, typically, an optical fiber. A semiconductor optical amplifier (hereafter denoted as SOA) is usually set in the front end of the optical receiver to amplify the weakened incoming optical signal. An SOA evens a level of the optical signal to be suitable for the optical devices set in the downstream of the optical de-multiplexer even when only one of parts of the incoming optical signal is lost and the level thereof is lowered. Then, the data recovered from the transmitted data becomes meaningless.